In the art of container closures, solid wooden bungs and to some extent molded plastic bungs have been used to close off the bung orifice in a pressurized beer barrel. Among the disadvantages of the wooden bung is the fact that it in general is subject to all of the vicissitudes of a product of nature, it is moisture sensitive and will swell or contract, it may have holes, it is subject to spalling, all of which may result in leakage of pressure. Moreover, wooden bungs do not readily release or blow out under extreme or dangerous tank pressures where a blow out would be desirable. Molded plastic bungs on the other hand have the advantage of overcoming the above deficiencies inherent in a product of nature and may be made using rapid, low cost molding techniques.
In providing molded plastic bungs, consideration must be given to providing sufficient strength to allow the bung to be driven into place in the barrel without breakage and at the same time afford a pressure seal that will not malfunction under internal pressure even if the barrel is dropped and yet is capable of affording a release in the event tank pressures become excessively or dangerously high. Moreover, the bung must be sufficiently strong to facilitate its ready removal in its entirety with a removal tool. Examples of prior plastic bungs are shown and described in U.S. Pat. Nos. 3,381,841 and 3,476,686 and D-216,678 which are assigned to the assignee of the present invention. In these earlier patents, there is provided hollow outer shell shaped to be inserted into the bung orifice with an external surface that forms a pressure seal with the bung orifice wall together with a generally transverse closure head that is arranged so that there is a flexure in the closure head in response to placing the closure head under compression and also in response to its fluid pressure in the barrel to urge the outer shell against the bung orifice to further increase the sealing effect of the bung in the barrel hole. It is noted however that the closure head of these prior patents is not arranged along a continuous line from the attachment to the inside of the outer shell to the center but that opposed sections of the closure head have different spaced swivel points that are separated by a dome-shaped central cap forming a bottom of the column.
Accordingly, it is a general object of the present invention to provide a novel and improved bung that is particularly suitable for pressurized beer barrels.
Another object of this invention is to provide an improved bung for a pressurized barrel chiefly characterized by durability, minimizing of materials and of a construction that is easily molded from plastic without significant distortion.
Yet a further object of this invention is to provide an improved bung for a pressurized barrel that is made entirely of a resilient and yieldable thermoplastic material and is constructed to yield radially inwardly toward its center upon insertion into a typical bung orifice and expand radially outwardly away from its center due to construction and inherent resiliency of the material and also to barrel pressure to increase the sealing effect of the bung in the barrel orifice to maintain a seal even to dynamic pressure as when the barrel is dropped or the like.
Another object of this invention is to provide an improved bung for a barrel that is readily installed by means of an impact tool, seals effectively against leakage of the barrel under normal pressures, is self regulating in that the bung will leak to relieve barrel pressures during pressures that are higher than normal barrel pressures and will blow out in the event of sudden intense pressure buildup or dangerous tank pressures and further a bung that may be normally easily removed by a removal tool.
Still a further object of the present invention is to provide a novel and improved bung generally characterized by a resilient, substantially hollow outer shell that seals against the wall of the bung hole and a resilient transverse closure head extending inwardly from the inside of the outer shell arranged on a true normal or an incline from the outer attached edge toward the center in a continuous line to flex inwardly in a toggle-like action in response to inherent resiliency of the material and in response to barrel pressure to increase the sealing effect.
Yet another object of this invention is to provide a novel and improved bung for a pressurized barrel in which concentric column structure is provided on the transverse closure head to reinforce the closure head and to provide a means to reverse the closure head by concentrically uniform forces to facilitate the axially directed pulling removal of the bung by a bung removal tool.
A further object is to provide a bung that is constructed so that double drives may be readily removed from the barrel.